Tuning electrodes used in a reactor for electrochemically processing a microelectronic workpiece

ABSTRACT

A facility for selecting and refining electrical parameters for processing a microelectronic workpiece in a processing chamber is described. The facility initially configures the electrical parameters in accordance with either a mathematical model of the processing chamber or experimental data derived from operating the actual processing chamber. After a workpiece is processed with the initial parameter configuration, the results are measured and a sensitivity matrix based upon the mathematical model of the processing chamber is used to select new parameters that correct for any deficiencies measured in the processing of the first workpiece. These parameters are then used in processing a second workpiece, which may be similarly measured, and the results used to further refine the parameters. In some embodiments, the facility analyzes a profile of the seed layer applied to a workpiece, and determines and communicates to a material deposition tool a set of control parameters designed to deposit material on the workpiece in a manner that compensates for deficiencies in the seed layer.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 09/849,505, filed May 4, 2001, which claims thebenefit of U.S. Provisional Patent Application No. 60/206,663, filed May24, 2000, and which is a continuation-in-part of International PatentApplication No. PCT/US00/10120, filed Apr. 13, 2000, designating theUnited States and claiming the benefit of U.S. Provisional PatentApplication Nos. 60/182,160, filed Feb. 14, 2000, 60/143,769, filed Jul.12, 1999, and 60/129,055, filed Apr. 13, 1999; and this applicationclaims the benefit of provisional application No. 60/206,663, filed May24, 2000; the disclosures of each of which are hereby expresslyincorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention is directed to the field of automatic processcontrol, and, more particularly, to the field of controlling a materialdeposition process.

BACKGROUND OF THE INVENTION

The fabrication of microelectronic components from a microelectronicworkpiece, such as a semiconductor wafer substrate, polymer substrate,etc., involves a substantial number of processes. For purposes of thepresent application, a microelectronic workpiece is defined to include aworkpiece formed from a substrate upon which microelectronic circuits orcomponents, data storage elements or layers, and/or micro-mechanicalelements are formed. There are a number of different processingoperations performed on the microelectronic workpiece to fabricate themicroelectronic component(s). Such operations include, for example,material deposition, patterning, doping, chemical mechanical polishing,electropolishing, and heat treatment.

Material deposition processing involves depositing or otherwise formingthin layers of material on the surface of the microelectronic workpiece.Patterning provides selective deposition of a thin layer and/or removalof selected portions of these added layers. Doping of the semiconductorwafer, or similar microelectronic workpiece, is the process of addingimpurities known as “dopants” to selected portions of the wafer to alterthe electrical characteristics of the substrate material. Heat treatmentof the microelectronic workpiece involves heating and/or cooling theworkpiece to achieve specific process results. Chemical mechanicalpolishing involves the removal of material through a combinedchemical/mechanical process while electropolishing involves the removalof material from a workpiece surface using electrochemical reactions.

Numerous processing devices, known as processing “tools,” have beendeveloped to implement one or more of the foregoing processingoperations. These tools take on different configurations depending onthe type of workpiece used in the fabrication process and the process orprocesses executed by the tool. One tool configuration, known as theLT-210C™ processing tool and available from Semitool, Inc., ofKalispell, Mont., includes a plurality of microelectronic workpieceprocessing stations that are serviced by one or more workpiece transferrobots. Several of the workpiece processing stations utilize a workpieceholder and a process bowl or container for implementing wet processingoperations. Such wet processing operations include electroplating,etching, cleaning, electroless deposition, electropolishing, etc. Inconnection with the present invention, it is the electrochemicalprocessing stations used in the LT-210C™ that are noteworthy. Suchelectrochemical processing stations perform the foregoingelectroplating, electropolishing, anodization, etc., of themicroelectronic workpiece. It will be recognized that theelectrochemical processing system set forth herein is readily adapted toimplement each of the foregoing electrochemical processes.

In accordance with one configuration of the LT-210C™ tool, theelectrochemical processing stations include a workpiece holder and aprocess container that are disposed proximate one another. The workpieceholder and process container are operated to bring the microelectronicworkpiece held by the workpiece holder into contact with anelectrochemical processing fluid disposed in the process container. Whenthe microelectronic workpiece is positioned in this manner, theworkpiece holder and process container form a processing chamber thatmay be open, enclosed, or substantially enclosed.

Electroplating and other electrochemical processes have become importantin the production of semiconductor integrated circuits and othermicroelectronic devices from microelectronic workpieces. For example,electroplating is often used in the formation of one or more metallayers on the workpiece. These metal layers are often used toelectrically interconnect the various devices of the integrated circuit.Further, the structures formed from the metal layers may constitutemicroelectronic devices such as read/write heads, etc.

Electroplated metals typically include copper, nickel, gold, platinum,solder, nickel-iron, etc. Electroplating is generally effected byinitial formation of a seed layer on the microelectronic workpiece inthe form of a very thin layer of metal, whereby the surface of themicroelectronic workpiece is rendered electrically conductive. Thiselectro-conductivity permits subsequent formation of a blanket orpatterned layer of the desired metal by electroplating. Subsequentprocessing, such as chemical mechanical planarization, may be used toremove unwanted portions of the patterned or metal blanket layer formedduring electroplating, resulting in the formation of the desiredmetallized structure.

Electropolishing of metals at the surface of a workpiece involves theremoval of at least some of the metal using an electrochemical process.The electrochemical process is effectively the reverse of theelectroplating reaction and is often carried out using the same orsimilar reactors as electroplating.

Anodization typically involves oxidizing a thin-film layer at thesurface of the workpiece. For example, it may be desirable toselectively oxidize certain portions of a metal layer, such as a Culayer, to facilitate subsequent removal of the selected portions in asolution that etches the oxidized material faster than the non-oxidizedmaterial. Further, anodization may be used to deposit certain materials,such as perovskite materials, onto the surface of the workpiece.

As the size of various microelectronic circuits and componentsdecreases, there is a corresponding decrease in the manufacturingtolerances that must be met by the manufacturing tools. In connectionwith the present invention as described below, electrochemical processesmust uniformly process the surface of a given microelectronic workpiece.Further, the electrochemical process must meet workpiece-to-workpieceuniformity requirements.

Electrochemical processes may be conducted in reaction chambers havingeither a single electrode or multiple electrodes. Where asingle-electrode reaction chamber is used, improving the leveluniformity achieved by the process often involves manual trial-and-errormodifications to the hardware configuration of the reaction chamber. Forexample, operators of the process may experiment with repositioning orreorienting the electrode, the workpiece, or a baffle separating theelectrode from the workpiece, or may modify aspects of a fluid flowwithin the reaction chamber in attempts to improve the level uniformityachieved by the process.

In a multiple-electrode reaction chamber, two or more electrodes arearranged in some pattern. Each of the electrodes is connected to anelectrical power supply that provides the electrical power used toexecute the electrochemical processing operations. Preferably, at leastsome of the electrodes are connected to different electrical nodes sothat the electrical power provided to them by the power supply may beprovided independent of the electrical power provided to otherelectrodes in the array.

Electrode arrays having a plurality of electrodes facilitate localizedcontrol of the electrical parameters used to electrochemically processthe microelectronic workpiece. This localized control of the electricalparameters can be used to provide greater uniformity of theelectrochemical processing across the surface of the microelectronicworkpiece when compared to single electrode systems withoutnecessitating hardware changes. However, determining the electricalparameters for each of the electrodes in the array to achieve thedesired process uniformity can be problematic. Typically, the electricalparameter (i.e., electrical current, voltage, etc.) for a givenelectrode in a given electrochemical process is determinedexperimentally using a manual trial and error approach.

Using such a manual trial and error approach, however, can be verytime-consuming. Further, the electrical parameters do not easilytranslate to other electrochemical processes. For example, a given setof electrical parameters used to electroplate a metal to a thickness Xonto the surface of a microelectronic workpiece cannot easily be used toderive the electrical parameters used to electroplate a metal to athickness Y. Still further, the electrical parameters used toelectroplate a desired film thickness X of a given metal (e.g., copper)are generally not suitable for use in electroplating another metal(e.g., platinum). Similar deficiencies in this trial and error approachare associated with other types of electrochemical processes (i.e.,anodization, electropolishing, etc.). Also, this manual trial and errorapproach often must be repeated in several common circumstances, such aswhen the thickness or level of uniformity of the seed layer changes,when the target plating thickness or profile changes, or when theplating rate changes.

In view of the foregoing, a system for electrochemically processing amicroelectronic workpiece that can be used to automatically identifyelectrical parameters that cause a multiple electrode array to achieve ahigh level of uniformity for a wide range of electrochemical processingvariables (e.g., seed layer thicknesses, seed layer types,electroplating materials, etc.) would have significant utility.

In the following, a facility for automatically identifying electricalparameters that produce a high level of uniformity in electrochemicallyprocessing a microelectronic workpiece is described. Embodiments of thisfacility are adapted to accommodate various electrochemical processes;reactor designs and conditions; plating materials and solutions;workpiece dimensions, materials, and conditions, and the nature andcondition of existing coatings on the workpiece. Accordingly, use of thefacility may typically result in substantial automation ofelectrochemical processing, even where a large number of variables indifferent dimensions are present. Such automation has the capacity toreduce the cost of skilled labor required to oversee a processingoperation, as well as increase output quality and throughput.Additionally, use of the facility can both streamline and improve theprocess of designing new electroplating reactors.

In one exemplary embodiment, the facility selects and refines electricalparameters for processing a microelectronic workpiece in a processingchamber. The facility initially configures the electrical parameters inaccordance with either a mathematical model of the processing chamber orexperimental data derived from operating the actual processing chamber.After a workpiece is processed with the initial parameter configuration,the results are measured and a sensitivity matrix based upon themathematical model of the processing chamber is used to select newparameters that correct for any deficiencies measured in the processingof the first workpiece. These parameters are then used in processing asecond workpiece, which may be similarly measured, and the results usedto further refine the parameters.

In another exemplary embodiment, the facility utilizes a sensitivitymatrix data structure. The sensitivity matrix data structure relates toa deposition chamber for depositing material on a workpiece. Thedeposition chamber has a number of deposition initiators, associatedwith each of which is a control parameter. For example, the depositionchamber may have deposition initiators that are electrodes, whosecontrol parameters are electrical current levels or other controlparameters. The data structure contains a number of quantitativeentries, each of which predicts, for a given change in the controlparameter associated with a given deposition initiator, the expectedchange in deposited material thickness at a given radius. The contentsof this data structure may be used to determine revised depositioninitiator parameters for better conforming deposited materialthicknesses to a target profile for deposited material thicknesses.

In another exemplary embodiment, the facility utilizes a materialdeposition process data structure, which contains a set of parametervalues used in a lo material deposition process. These parameters havebeen generated by adjusting an earlier-used set of parameters to resolvedifferences between measurements of a workpiece deposited using theearlier-used set of parameters in a target deposition profile specifiedfor the deposition process. The contents of this data structure may beused to deposit an additional workpiece in great conformance with thespecified deposition profile.

In another exemplary embodiment, the facility controls an electroplatingprocess having multiple steps, which is performed in an electroplatingchamber having a number of electrodes. For each electrode, the facilitydetermines the net plating charge delivered through the electrode duringa first plating cycle to plate a first workpiece. This is accomplishedby summing the plating charges delivered through the electrode in eachstep of the process. The facility then compares a plating profileachieved in plating the first workpiece to a target plating profile. Insuch comparison, the facility identifies deviations between the achievedplating profile and the target plating profile. The facility determinesnew net plating charges for each electrode selected to reduce theidentified deviations in the second workpiece. For each of these new netplating charges, the facility distributes the new net plating chargeacross the steps of the process, and uses the distributed new netplating charges to determine a current for each electrode for each stepof the process. A second plating cycle may then be conducted to plate asecond workpiece using the currents determined for each electrode foreach step.

In another exemplary embodiment, the facility evaluates a design for anelectroplating reactor. The facility first applies a mathematical modelembodying the reactor design to a set of initial electrode current todetermine a first resulting plating profile. The facility compares thefirst resulting plating profile to a target plating profile to obtain afirst difference. The facility then applies a sensitivity technique toidentify a set of revised electrode currents, and applies themathematical model to the set of revised electrode currents to determinea second resulting plating profile. The facility compares the secondresulting plating profile to the target plating profile to obtain asecond difference, and evaluates the design based on the obtained seconddifference.

In another exemplary embodiment, the facility is embodied in anapparatus for selecting parameters for use in controlling operation of adeposition chamber to deposit material on a selected wafer in a way thatoptimizes conformity with a specified deposition pattern. The apparatusincludes a measurement receiving subsystem that receives the followingmeasurements: pre-deposition thicknesses of the selected wafer beforematerial is deposited on the wafer; post-deposition thicknesses of analready-deposited wafer after material is deposited on thealready-deposited wafer; and pre-deposition thicknesses of thealready-deposited wafer before material is deposited on the wafer. Theapparatus further includes a parameter selection subsystem that selectsthe parameters to be used to deposit material on the selected waferbased on the specified deposition pattern, the pre-depositionthicknesses of the selected wafer, the pre-deposition thicknesses of thealready-deposited wafer, parameters used for depositing material on thealready-deposited wafer, and the post-deposition thicknesses of thealready-deposited wafer.

In another exemplary embodiment, the facility electroplates a selectedsurface using a plurality of electrodes. The facility obtains a currentspecification set comprised of a plurality of current levels, eachspecified for a particular one of the plurality of electrodes. Thecurrent levels of the current specification set each represent amodification of current levels of a distinguished current specificationset, modified in order to improve results produced by electroplating inaccordance with the distinguished current specification set. For eachelectrode, the facility delivers the current level specified for theelectrode by the current specification set to the electrode in order toelectroplate the selected surface.

In another exemplary embodiment, the facility automatically configuresparameters usable to control operation of a reaction chamber toelectropolish a selected wafer in a way that optimizes conformity with aspecified electropolishing pattern. The facility receives pre-polishingthicknesses of the selected wafer before the selected wafer is polished.The facility also receives post-polishing thicknesses of analready-polished wafer the already-polished wafer is polished. Thefacility further receives pre-polishing thicknesses of thealready-polished wafer before the already-polished wafer is polished.The facility selects the parameters to polish the selected wafer basedon the specified polishing pattern, the pre-polishing thicknesses of theselected wafer, the pre-polishing thicknesses of the already-polishedwafer, parameters used for polishing the already-polished wafer, and thepost-polishing thicknesses of the already-polished wafer.

In another exemplary embodiment, the facility electroplates amicroelectronic workpiece. The facility receives data representing aprofile of a seed layer that has been applied to the workpiece, such asfrom a metrology station. The facility identifies deficiencies in theseed layer based upon the profile of the seed layer represented by thereceived data, and determines a set of control parameters for platingthe workpiece in a manner that compensates for the identifieddeficiencies in the seed layer. The facility communicates thisdetermined set of control parameters to a plating tool for use inplating the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process schematic diagram showing inputs and outputs of theoptimizer.

FIG. 2 is a process schematic diagram showing a branched correctionsystem utilized by some embodiments of the optimizer.

FIG. 3 is schematic block diagram of an electrochemical processingsystem constructed in accordance with one embodiment of the optimizer.

FIG. 4 is a flowchart illustrating one manner in which the optimizer ofFIG. 3 can use a predetermined set of sensitivity values to generate amore accurate electrical parameter set for use in meeting targetedphysical characteristics in the processing of a microelectronicworkpiece.

FIG. 5 is a graph of a sample Jacobian sensitivity matrix for amultiple-electrode reaction chamber.

FIG. 6 is a spreadsheet diagram showing the new current outputscalculated from the inputs for the first optimization run.

FIG. 7 is a spreadsheet diagram showing the new current outputscalculated from the inputs for the second optimization run.

DETAILED DESCRIPTION

A facility for automatically selecting and refining electricalparameters for processing a microelectronic workpiece (“the optimizer”)is disclosed. In many embodiments, the optimizer determines processparameters affecting the processing of a round workpiece as a functionof processing results at various radii on the workpiece. In someembodiments, the optimizer adjusts the electrode currents for a multipleelectrode electroplating chamber, such as multiple anode reactionchambers of the Paragon tool provided by Semitool, Inc. of Kalispell,Mont., in order to achieve a specified thickness profile (i.e., flat,convex, concave, etc.) of a coating, such as a metal or other conductor,applied to a semiconductor wafer. The optimizer adjusts electrodecurrents for successive workpieces to compensate for changes in thethickness of the seed layer of the incoming workpiece (a source of feedforward control), and/or to correct for non-uniformities produced inprior wafers at the anode currents used to plate them (a source offeedback control). In this way, the optimizer is able to quickly achievea high level of uniformity in the coating deposited on workpieceswithout substantial manual intervention.

The facility typically operates an electroplating chamber containing aprincipal fluid flow chamber, and a plurality of electrodes disposed inthe principal fluid flow chamber. The electroplating chamber typicallyfurther contains a workpiece holder positioned to hold at least onesurface of the microelectronic workpiece in contact with anelectrochemical processing fluid in the principal fluid flow chamber, atleast during electrochemical processing of the microelectronicworkpiece. One or more electrical contacts are configured to contact theat least one surface of the microelectronic workpiece, and an electricalpower supply is connected to the one or more electrical contacts and tothe plurality of electrodes. At least two of the plurality of electrodesare independently connected to the electrical power supply to facilitateindependent supply of power thereto. The apparatus also includes acontrol system that is connected to the electrical power supply tocontrol at least one electrical power parameter respectively associatedwith each of the independently connected electrodes. The control systemsets the at least one electrical power parameter for a given one of theindependently connected electrodes based on one or more user inputparameters and a plurality of predetermined sensitivity values; whereinthe sensitivity values correspond to process perturbations resultingfrom perturbations of the electrical power parameter for the given oneof the independently connected electrodes.

For example, although the present invention is described in the contextof electrochemical processing of the microelectronic workpiece, theteachings herein can also be extended to other types of microelectronicworkpiece processing. In effect, the teachings herein can be extended toother microelectronic workpiece processing systems that haveindividually controlled processing elements that are responsive tocontrol parameters and that have interdependent effects on a physicalcharacteristic of the microelectronic workpiece that is processed usingthe elements. Such systems may employ sensitivity tables or matrices asset forth herein and use them in calculations with one or more inputparameters sets to arrive at control parameter values that accuratelyresult in the targeted physical characteristic of the microelectronicworkpiece.

FIG. 1 is a process schematic diagram showing inputs and outputs of theoptimizer. FIG. 1 shows that the optimizer 140 uses up to three sourcesof input: baseline currents 110, seed change. 120, and thickness error130. The baseline currents 110 are the anode currents used to plate theprevious wafer or another set of currents for which plating thicknessresults are known. For the first workpiece in a sequence of workpieces,the baseline currents used to plate the wafer are typically specified bya source other than the optimizer. For example, they may be specified bya recipe used to plate the wafers, or may be manually determined.

The seed change 120 is the difference between the thickness of the loseed layer of the incoming wafer 121 and the thickness of the seed layerof the previous plated wafer 122. The seed change input 120 is said tobe a source of feed-forward control in the optimizer, in that itincorporates information about the upcoming plating cycle, as itreflects the measurement the wafer to be plated in the upcoming platingcycle. Thickness error 130 is the difference in thickness between theprevious plated wafer 132 and the target thickness profile 131 specifiedfor the upcoming plating cycle. The thickness error 130 is said to be asource of feedback control, because it incorporates information from anearlier plating cycle, that is, the thickness of the wafer plated in theprevious plating cycle.

FIG. 1 further shows that the optimizer outputs new plating charges 150for each electrode in the upcoming plating cycle, expressed inamp-minute units. The new plating charges output is combined with arecipe schedule and a current waveform 161 to generate the currents 162,in amps, to be delivered through each electrode at each point in therecipe schedule. These new currents are used by the plating process toplate a wafer in the next plating cycle. In embodiments in whichdifferent types of power supplies are used, other types of controlparameters are generated by the optimizer for use in operating the powersupply. For example, where a voltage control power supply is used, thecontrol parameters generated by the optimizer are voltages, expressed involts. The wafer so plated is then subjected to post-plating metrologyto measure its plated thickness 132.

While the optimizer is shown as receiving inputs and producing outputsat various points in the processing of these values, it will beunderstood by those in the art that the optimizer may be variouslydefined to include or exclude aspects of such processing. For example,while FIG. 1 shows the generation of seed change from baseline waferseed thickness and seed layer thickness outside the optimizer, it iscontemplated that such generation may alternatively be performed withinthe optimizer.

FIG. 2 is a process schematic diagram showing a branched correctionsystem utilized by some embodiments of the optimizer. The branchedadjustment system utilizes two independently-engageable correctionadjustments, a feedback adjustment (230, 240, 272) due to thicknesserrors and a feed forward adjustment (220, 240, 271) due to incomingseed layer thickness variation. When the anode currents produce anacceptable uniformity, the feedback loop may be disengaged from thetransformation of baseline currents 210 to new currents 280. The feedforward compensation may be disengaged in situations where the seedlayer variations are not expected to affect thickness uniformity. Forexample, after the first wafer of a similar batch is corrected for, thefeed-forward compensation may be disengaged and the corrections may beapplied to each sequential wafer in the batch.

FIG. 3 is schematic block diagram of an electrochemical processingsystem constructed in accordance with one embodiment of the optimizer.FIG. 3 shows a reactor assembly 20 for electrochemically processing amicroelectronic workpiece 25, such as a semiconductor wafer, that can beused in connection with the present invention. Generally stated, anembodiment of the reactor assembly 20 includes a reactor head 30 and acorresponding reactor base or container shown generally at 35. Thereactor base 35 can be a bowl and cup assembly for containing a flow ofan electrochemical processing solution. The reactor 20 of FIG. 3 can beused to implement a variety of electrochemical processing operationssuch as electroplating, electropolishing, anodization, etc., as well asto implement a wide variety of other material deposition techniques. Forpurposes of the following discussion, aspects of the specific embodimentset forth herein will be described, without limitation, in the contextof an electroplating process.

The reactor head 30 of the reactor assembly 20 can include a stationaryassembly (not shown) and a rotor assembly (not shown). The rotorassembly may be configured to receive and carry an associatedmicroelectronic workpiece 25, position the microelectronic workpiece ina process-side down orientation within reactor container 35, and torotate or spin the workpiece. The reactor head 30 can also include oneor more contacts 85 (shown schematically) that provide electroplatingpower to the surface of the microelectronic workpiece. In theillustrated embodiment, the contacts 85 are configured to contact a seedlayer or other conductive material that is to be plated on the platingsurface microelectronic workpiece 25. It will be recognized, however,that the contacts 85 can engage either the front side or the backside ofthe workpiece depending upon the appropriate conductive path between thecontacts and the area that is to be plated. Suitable reactor heads 30with contacts 85 are disclosed in U.S. Pat. No. 6,080,291 and U.S.application Ser. Nos. 09/386,803; 09/386,610; 09/386,197; 09/717,927;and 09/823,948, all of which are expressly incorporated herein in theirentirety by reference.

The reactor head 30 can be carried by a lift/rotate apparatus thatrotates the reactor head 30 from an upwardly-facing orientation in whichit can receive the microelectronic workpiece to a downwardly facingorientation in which the plating surface of the microelectronicworkpiece can contact the electroplating solution in reactor base 35.The lift/rotate apparatus can bring the workpiece 25 into contact withthe electroplating solution either coplanar or at a given angle. Arobotic system, which can include an end effector, is typically employedfor loading/unloading the microelectronic workpiece 25 on the head 30.It will be recognized that other reactor assembly configurations may beused with the inventive aspects of the disclosed reactor chamber, theforegoing being merely illustrative.

The reactor base 35 can include an outer overflow container 37 and aninterior processing container 39. A flow of electroplating fluid flowsinto the processing container 39 through an inlet 42 (arrow I). Theelectroplating fluid flows through the interior of the processingcontainer 39 and overflows a weir 44 at the top of processing container39 (arrow F). The fluid overflowing the weir 44 then passes through anoverflow container 37 and exits the reactor 20 through an outlet 46(arrow O). The fluid exiting the outlet 46 may be directed to arecirculation system, chemical replenishment system, disposal system,etc.

The reactor 20 also includes an electrode in the processing container 39to contact the electrochemical processing fluid (e.g., theelectroplating fluid) as it flows through the reactor 20. In theembodiment of FIG. 3, the reactor 20 includes an electrode assembly 50having a base member 52 through which a plurality of fluid flowapertures 54 extend. The fluid flow apertures 54 assist in disbursingthe electroplating fluid flow entering inlet 42 so that the flow ofelectroplating fluid at the surface of microelectronic workpiece 25 isless localized and has a desired radial distribution. The electrodeassembly 50 also includes an electrode array 56 that can comprise aplurality of individual electrodes 58 supported by the base member 52.The electrode array 56 can have several configurations, including thosein which electrodes are disposed at different distances from themicroelectronic workpiece. The particular physical configuration that isutilized in a given reactor can depend on the particular type and shapeof the microelectronic workpiece 25. In the illustrated embodiment, themicroelectronic workpiece 25 is a disk-shaped semiconductor wafer.Accordingly, the present inventors have found that the individualelectrodes 58 may be formed as rings of different diameters and thatthey may be arranged concentrically in alignment with the center ofmicroelectronic workpiece 25. It will be recognized, however, that gridarrays or other electrode array configurations may also be employedwithout departing from the scope of the present invention. One suitableconfiguration of the reactor base 35 and electrode array 56 is disclosedin U.S. Ser. No. 09/804,696, filed Mar. 12, 2001 (Attorney Docket No.29195.8119US), while another suitable configuration is disclosed in U.S.Ser. No. 09/804,697, filed Mar. 12, 2001 (Attorney Docket No.29195.8120US), both of which are hereby incorporated by reference.

When the reactor 20 electroplates at least one surface ofmicroelectronic workpiece 25, the plating surface of the workpiece 25functions as a cathode in the electrochemical reaction and the electrodearray 56 functions as an anode. To this end, the plating surface ofworkpiece 25 is connected to a negative potential terminal of a powersupply 60 through contacts 85 and the individual electrodes 58 of theelectrode array 56 are connected to positive potential terminals of thesupply 60. In the illustrated embodiment, each of the individualelectrodes 58 is connected to a discrete terminal of the supply 60 sothat the supply 60 may individually set and/or alter one or moreelectrical parameters, such as the current flow, associated with each ofthe individual electrodes 58. As such, each of the individual electrodes58 of FIG. 3 is an individually controllable electrode. It will berecognized, however, that one or more of the individual electrodes 58 ofthe electrode array 56 may be connected to a common node/terminal of thepower supply 60. In such instances, the power supply 60 will alter theone or more electrical parameters of the commonly connected electrodes58 concurrently, as opposed to individually, thereby effectively makingthe commonly connected electrodes 58 a single, individually controllableelectrode. As such, individually controllable electrodes can bephysically distinct electrodes that are connected to discrete terminalsof power supply 60 as well as physically distinct electrodes that arecommonly connected to a single discrete terminal of power supply 60. Theelectrode array 56 preferably comprises at least two individuallycontrollable electrodes.

The electrode array 56 and the power supply 60 facilitate localizedcontrol of the electrical parameters used to electrochemically processthe microelectronic workpiece 25. This localized control of theelectrical parameters can be used to enhance the uniformity of theelectrochemical processing across the surface of the microelectronicworkpiece when compared to a single electrode system. Unfortunately,determining the electrical parameters for each of the electrodes 58 inthe array 56 to achieve the desired process uniformity can be difficult.The optimizer, however, simplifies and substantially automates thedetermination of the electrical parameters associated with each of theindividually controllable electrodes. In particular, the optimizerdetermines a plurality of sensitivity values, either experimentally orthrough numerical simulation, and subsequently uses the sensitivityvalues to adjust the electrical parameters associated with each of theindividually controllable electrodes. The sensitivity values may beplaced in a table or may be in the form of a Jacobian matrix. Thistable/matrix holds information corresponding to process parameterchanges (i.e., thickness of the electroplated film) at various points onthe workpiece 25 due to electrical parameter perturbations (i.e.,electrical current changes) to each of the individually controllableelectrodes. This table/matrix is derived from data from a baselineworkpiece plus data from separate runs with a perturbation of acontrollable electrical parameter to each of the individuallycontrollable electrode.

The optimizer typically executes in a control system 65 that isconnected to the power supply 60 in order to supply current values for aplating cycle. The control system 65 can take a variety of forms,including general- or special-purpose computer systems, eitherintegrated into the manufacturing tool containing the reaction chamberor separate from the manufacturing tool, such as a laptop or otherportable computer system. The control system may be communicativelyconnected to the power supply 60, or may output current values that arein turn manually inputted to the power supply. Where the control systemis connected to the power supply by a network, other computer systemsand similar devices may intervene between the control system and thepower supply. In many embodiments, the control system” contains suchcomponents as one or more processors, a primary memory for storingprograms and data, a persistent memory for persistently storing programsand data, input/output devices, and a computer-readable medium drive,such as a CD-ROM drive or a DVD drive.

Once the values for the sensitivity table/matrix have been determined,the values may be stored in and used by control system 65 to control oneor more of the electrical parameters that power supply 60 uses inconnection with each of the individually controllable electrodes 58.FIG. 4 is a flow diagram illustrating one manner in which thesensitivity table/matrix may be used to calculate an electricalparameter (i.e., current) for each of the individually controllableelectrodes 58 that may be used to meet a process target parameter (i.e.,target thickness of the electroplated film).

In the steps shown in FIG. 4, the optimizer utilizes two sets of inputparameters along with the sensitivity table/matrix to calculate therequired electrical parameters. In step 70, the optimizer performs afirst plating cycle (a “test run”) using a known, predetermined set ofelectrical parameters. For example, a test run can be performed bysubjecting a microelectronic workpiece 25 to an electroplating processin which the current provided to each of the individually controllableelectrodes 58 is fixed at a predetermined magnitude for a given periodof time.

In step 72, after the test run is complete, the optimizer measures thephysical characteristics (i.e., thickness of the electroplated film) ofthe test workpiece to produce a first set of parameters. For example, instep 72, the test workpiece may be subjected to thickness measurementsusing a metrology station, producing a set of parameters containingthickness measurements at each of a number of points on the testworkpiece. In step 74, the optimizer compares the physicalcharacteristics of the test workpiece measured in step 72 against asecond set of input parameters. In the illustrated embodiment of themethod, the second set of input parameters corresponds to the targetphysical characteristics of the microelectronic workpiece that are to beultimately achieved by the process (i.e., the thickness of theelectroplated film). Notably, the target physical characteristics caneither be uniform over the surface of the microelectronic workpiece 25or vary over the surface. For example, in the illustrated embodiment,the thickness of an electroplated film on the surface of themicroelectronic workpiece 25 can be used as the target physicalcharacteristic, and the user may expressly specify the targetthicknesses at various radial distances from the center of theworkpiece, a grid relative to the workpiece, or other reference systemsrelative to fiducials on the workpiece.

In step 74, the optimizer uses the first and second set of inputparameters to generate a set of process error values. In step 80, theoptimizer derives a new electrical parameter set based on calculationsincluding the set of process error values and the values of thesensitivity table/matrix. In step 82, once the new electrical parameterset is derived, the optimizer directs power supply 60 to use the derivedelectrical parameters in processing the next microelectronic workpiece.Then, in step 404, the optimizer measures physical characteristics ofthe test workpiece in a manner similar to step 72. In step 406, theoptimizer compares the characteristics measured in step 404 with a setof target characteristics to generate a set of process error values. Theset of target characteristics may be the same set of targetcharacteristics as used in step 74, or may be a different set of targetcharacteristics. In step 408, if the error values generated in step 406are within a predetermined range, then the optimizer continues in step410, else the facility continues in 80. In step 80, the optimizerderives a new electrical parameter set. In step 410, the optimizer usesthe newest electrical parameter derived in step 80 in processingsubsequent microelectronic workpieces. In some embodiments (not shown),the processed microelectronic workpieces, and/or their measuredcharacteristics are examined, either manually or automatically, in orderto further troubleshoot the process.

With reference again to FIG. 3, the first and second set of inputparameters may be provided to the control system 65 by a user interface64 and/or a metrics tool 86. The user interface 64 can include akeyboard, a touch-sensitive screen, a voice recognition system, and/orother input devices. The metrics tool 86 may be an automated tool thatis used to measure the physical characteristics of the test workpieceafter the test run, such as a metrology station. When both a userinterface 64 and a metrics tool 86 are employed, the user interface 64may be used to input the target physical characteristics that are to beachieved by the process while metrics tool 86 may be used to directlycommunicate the measured physical characteristics of the test workpieceto the control system 65. In the absence of a metrics tool that cancommunicate with control system 65, the measured physicalcharacteristics of the test workpiece can be provided to control system65 through the user interface 64, or by removable data storage media,such as a floppy disk. It will be recognized that the foregoing are onlyexamples of suitable data communications devices and that other datacommunications devices may be used to provide the first and second setof input parameters to control system 65.

In order to predict change in thickness as a function of change incurrent, the optimizer generates a Jacobian sensitivity matrix. Anexample in which the sensitivity matrix generated by the optimizer isbased upon a mathematical model of the reaction chamber is discussedbelow. In additional embodiments, however, the sensitivity matrix usedby the optimizer is based upon experimental results produced byoperating the actual reaction chamber. The data modeled in thesensitivity matrix includes a baseline film thickness profile and asmany perturbation curves as anodes, where each perturbation curveinvolves adding roughly 0.05 amps to one specific anode. The Jacobian isa matrix of partial derivatives, representing the change in thickness inmicrons over the change in current in amp minutes. Specifically, theJacobian is an m×n matrix where m, the number of rows, is equal to thenumber of radial location data points in the modeled data and n, thenumber of columns, is equal to the number of anodes on the reactor.Typically, the value of m is relatively large (>100) due to thecomputational mesh chosen for the model of the chamber. The componentsof the matrix are calculated by taking the quotient of the difference inthickness due to the perturbed anode and the current change inamp-minutes, which is the product of the current change in amps and therun time in minutes.

As one source of feedback control, the optimizer uses the thickness ofthe most-recently plated wafer at each of a number of radial positionson the plated wafer. These radial positions may either be selected fromthe radial positions corresponding to the rows of the matrix, or may beinterpolated between the radial positions corresponding to the rows ofthe matrix. A wide range of numbers of radial positions may be used. Asthe number of radial positions used increases, the optimizer's resultsin terms of coating uniformity improves. However, as the number ofradial positions used increases, the amount of time required to measurethe wafer, to input the measurement results, and/or to operate theoptimizer to generate new currents can increase. Accordingly, thesmallest number of radial positions that produce acceptable results istypically used. One approach is to use the number of radial test pointswithin a standard metrology contour map (4 for 200 mm and 4 or 6 for 300mm) plus one, where the extra point is added to better the 3 sigmauniformity for all the points (i.e., to better the diameter scan).

A specific measurement point map may be designed for the metrologystation, which will measure the appropriate points on the wafercorresponding with the radial positions necessary for the optimizeroperation.

The optimizer can further be understood with reference to a specificembodiment in which the electrochemical process is electroplating, thethickness of the electroplated film is the target physical parameter,and the current provided to each of the individually controlledelectrodes 58 is the electrical parameter that is to be controlled toachieve the target film thickness. In accordance with this specificembodiment, a Jacobian sensitivity matrix is first derived fromexperimental or numerically simulated data. FIG. 5 is a graph of asample Jacobian sensitivity matrix for a multiple-electrode reactionchamber. In particular, FIG. 5 is a graph of a sample change inelectroplated film thickness per change in current-time as a function ofradial position on the microelectronic workpiece 25 for each of a numberof individually controlled electrodes, such as anodes A1-A4 shown inFIG. 3. A first baseline workpiece is electroplated for a predeterminedperiod of time by delivering a predetermined set of current values toelectrodes in the multiple anode reactor. The thickness of the resultingelectroplated film is then measured as a function of the radial positionon the workpiece. These data points are then used as baselinemeasurements that are compared to the data acquired as the current toeach of the anodes A1-A4 is perturbated. Line 90 is a plot of theJacobian terms associated with a perturbation in the current provided bypower supply 60 to anode Al with the current to the remaining anodesA2-A4 held at their constant predetermined values. Line 92 is a plot ofthe Jacobian terms associated with a perturbation in the currentprovided by power supply 60 to anode A2 with the current to theremaining anodes A1 and A3-A4 held at their constant predeterminedvalues. Line 94 is a plot of the Jacobian terms associated with aperturbation in the current provided by power supply 60 to anode A3 withthe current to the remaining anodes A1-A2 and A4 held at their constantpredetermined values. Lastly, line 96 is a plot of the Jacobian termsassociated with a perturbation in the current provided by power supply60 to anode A4 with the current to the remaining anodes A1-A3 held attheir constant predetermined values.

The data for the Jacobian parameters shown in FIG. 5 may be computedusing the following equations: $\begin{matrix}{J_{ij} = {\frac{\partial t_{i}}{\partial{AM}_{j}} \cong \frac{{t_{i}\left( {{AM} + ɛ_{j}} \right)} - {t_{i}({AM})}}{ɛ_{j}}}} & {{Equation}\quad({A1})} \\{{t({AM})} = \begin{bmatrix}{t_{1}({AM})} & {t_{2}({AM})} & \ldots & {t_{m}({AM})}\end{bmatrix}} & {{Equation}\quad({A2})} \\{{AM} = \begin{bmatrix}{AM}_{1} & {AM}_{2} & \cdots & {AM}_{n}\end{bmatrix}} & {{Equation}\quad({A3})} \\\begin{matrix}{ɛ_{1} = \begin{bmatrix}{\Delta\quad{AM}_{1}} \\0 \\. \\. \\0\end{bmatrix}} & {ɛ_{2} = \begin{bmatrix}0 \\{\Delta\quad{AM}_{2}} \\0 \\. \\0\end{bmatrix}} & \ldots & {ɛ_{n} = \begin{bmatrix}0 \\. \\. \\0 \\{\Delta\quad{AM}_{n}}\end{bmatrix}}\end{matrix} & {{Equation}\quad({A4})}\end{matrix}$where:

-   -   t represents thickness [microns];    -   AM represents current [amp-minutes];    -   ε represents perturbation [amp-minutes];    -   i is an integer corresponding to a radial position on the        workpiece;    -   j is an integer representing a particular anode;    -   m is an integer corresponding to the total number of radial        positions on the workpiece; and    -   n is an integer representing the total number of        individually-controllable anodes.

The Jacobian sensitivity matrix, set forth below as Equation (A5), is anindex of the Jacobian values computed using Equations (A1)-(A4). TheJacobian matrix may be generated either using a simulation of theoperation of the deposition chamber based upon a mathematical model ofthe deposition chamber, or using experimental data derived from theplating of one or more test wafers. Construction of such a mathematicalmodel, as well as its use to simulate operation of the modeleddeposition chamber, is discussed in detail in G. Ritter, P. McHugh, G.Wilson and T. Ritzdorf, “Two- and three-dimensional numerical modelingof copper electroplating for advanced ULSI metallization,” Solid StateElectronics, volume 44, issue 5, pp. 797-807 (May 2000), available fromhttp://www.elsevier.nl/gej-ng/10/30/25/29/28/27/article.pdf, alsoavailable fromhttp://journals.ohiolink.edu/pdflinks/01040215463800982.pdf.$\begin{matrix}{J = {\begin{matrix}0.192982 & 0.071570 & 0.030913 & 0.017811 \\0.148448 & 0.084824 & 0.039650 & 0.022264 \\0.066126 & 0.087475 & 0.076612 & 0.047073 \\0.037112 & 0.057654 & 0.090725 & 0.092239 \\0.029689 & 0.045725 & 0.073924 & 0.138040\end{matrix}}} & {{Equation}\quad({A5})}\end{matrix}$

The values in the Jacobian matrix are also presented as highlighted datapoints in the graph of FIG. 5. These values correspond to the radialpositions on the surface of a semiconductor wafer that are typicallychosen for measurement. Once the values for the Jacobian sensitivitymatrix have been derived, they may be stored in control system 65 forfurther use.

Table 1 below sets forth exemplary data corresponding to a test run inwhich a 200 mm wafer is plated with copper in a multiple anode systemusing a nominally 2000 Å thick initial copper seed-layer. Identicalcurrents of 1.12 Amps (for 3 minutes) were provided to all four anodesA1-A4. The resulting thickness at five radial locations was thenmeasured and is recorded in the second column of Table 1. The 3 sigmauniformity of the wafer is 9.4% using a 49 point contour map. Targetthickness were then provided and are set forth in column 3 of Table 1.In this example, because a flat coating is desired, the target thicknessis the same at each radial position. The thickness errors (processederrors) between the plated film and the target thickness were thencalculated and are provided in the last column of Table 1. Thesecalculated thickness errors are used by the optimizer as a source offeedback control. TABLE 1 DATA FROM WAFER PLATED WITH 1.12 AMPS TO EACHANODE. Radial Measured Target Location Thickness Thickness Error (m)(microns) (microns) (microns) 0 1.1081 1.0291 −0.0790 0.032 1.07781.0291 −0.0487 0.063 1.0226 1.0291 0.0065 0.081 1.0169 1.0291 0.01220.098 0.09987 1.0291 0.0304

The Jacobian sensitivity matrix may then be used along with thethickness error values to provide a revised set of anode current valuesthat should yield better film uniformity. The equations summarizing thisapproach are set fort below:

-   -   ΔAM=J⁻¹Δt (for a square system in which the Equation (B1) number        of measured radial positions corresponds to the number of        individually controlled anodes in the system); and    -   ΔAM=(J^(T)J)⁻¹J^(T)Δt (for a non-square system in which Equation        (B2) the number of measured radial positions is different than        the number of individually controlled anodes in the system).        Δt _(i) =t _(i) ^(target) −t _(i) ^(old)−(t _(i) ^(newseed) −t        ^(oldseed))+t_(i) ^(specified)   Equation (B3)

In Equation (B3), t_(i) ^(target) is the target thickness required toobtain a wafer of desired profile while considering the total currentadjustment, t_(i) ^(old) is the old overall thickness, t_(i) ^(newseed)is the thickness of the new seed layer, t_(i) ^(oldseed) is thethickness of the old seed layer, and t_(i) ^(specified) is the thicknessspecification relative to the center of the wafer, that is, thethickness specified by the target plating profile. In particular, theterm t_(i) ^(specified) represents the target thickness, while thequantity t_(i) ^(target)−t_(i) ^(oldseed) represents feedback from theprevious wafer, and the quantity t_(i) ^(newseed)−t_(i) ^(oldseed)represents feedforward from the thickness of the seed layer of theincoming wafer—to disable feedback control, the first quantity isomitted from equation (B3); to disable feedforward control, the secondquantity is omitted from equation (B3).

Table 2 shows the foregoing equations as applied to the given data setand the corresponding current changes that have been derived from theequations to meet the target thickness at each radial location (bestleast square fit). Such application of the equations, and constructionof the Jacobian matrix is in some embodiments performed using aspreadsheet application program, such as Microsoft Excel®, in connectionwith specialized macro programs. In other embodiments, differentapproaches are used in constructing the Jacobian matrix and applying theabove equations.

The wafer uniformity obtained with the currents in the last column ofTable 2 was 1.7% (compared to 9.4% for the test run wafer). Thisprocedure can be repeated again to try to further improve theuniformity. In this example, the differences between the seed layerswere ignored since the seed layers are substantially the same. TABLE 2CURRENT ADJUSTMENT Change to Anode Anode Anode Currents for CurrentsCurrents for Anode # Run #1 (Amps) (Amps) Run #2 (Amps) 1 1.12 −0.210.91 2 1.12 0.20 1.32 3 1.12 −0.09 1.03 4 1.12 0.10 1.22

Once the corrected values for the anode currents have been calculated,control system 65 of FIG. 3 directs power supply 60 to provide thecorrected current to the respective anode A1-A4 during subsequentprocesses to meet the target film thickness and uniformity.

In some instances, it may be desirable to iteratively apply theforegoing equations to arrive at a set of current change values (thevalues shown in column 3 of Table 2) that add up to zero. For example,doing so enables the total plating charge—and therefore the total massof plated material—to be held constant without having to vary the recipetime.

The Jacobian sensitivity matrix in the foregoing example quantifies thesystem response to anode current changes about a baseline condition.Ideally, a different matrix may be employed if the processing conditionsvary significantly from the baseline. The number of system parametersthat may influence the sensitivity values of the sensitivity matrix isquite large. Such system parameters include the seed layer thickness,the electrolyte conductivity, the metal being plated, the filmthickness, the plating rate, the contact ring geometry, the waferposition relative to the chamber, and the anode shape/currentdistribution. Anode shape/current distribution is included toaccommodate chamber designs where changes in the shape of consumableanodes over time affect plating characteristics of the chamber. Changesto all of these items can change the current density across the waferfor a given set of anode currents and, as a result, can change theresponse of the system to changes in the anode currents. It is expected,however, that small changes to many of these parameters will not requirethe calculation of a new sensitivity matrix. Nevertheless, a pluralityof sensitivity tables/matrices may be derived for different processingconditions and stored in control system 65. Which of the sensitivitytables/matrices is to be used by the control system 65 can be enteredmanually by a user, or can be set automatically depending onmeasurements taken by certain sensors or the like (i.e., temperaturesensors, chemical analysis units, etc.) that indicate the existence ofone or more particular processing conditions.

The optimizer may also be used to compensate for differences andnon-uniformities of the initial seed layer of the microelectronicworkpiece. Generally stated, a blanket seed layer can affect theuniformity of a plated film in two ways:

-   -   1. If the seed layer non-uniformity changes, this non-uniformity        is added to the final film. For example, if the seed layer is        100 Å thinner at the outer edge than expected, the final film        thickness may also be 100 Å thinner at the outer edge.    -   2. If the average seed-layer thickness changes significantly,        the resistance of the seed-layer will change resulting in a        modified current density distribution across the wafer and        altered film uniformity. For example, if the seed layer        decreases from 2000 Å to 1000 Å, the final film will not only be        thinner (because the initial film is thinner) but it will also        be relatively thicker at the outer edge due to the higher        resistivity of the 1000 Å seed-layer compared to the 2000 Å        seed-layer (assuming an edge contact).

The optimizer can be used to compensate for such seed-layer deviations,thereby utilizing seed-layer thicknesses as a source of feed-forwardcontrol. In the first case above, the changes in seed-layer uniformitymay be handled in the same manner that errors between target thicknessand measured thickness are handled. A pre-measurement of the waferquantifies changes in the seed-layer thickness at the various radialmeasurement locations and these changes (errors) are figured into thecurrent adjustment calculations. Using this approach, excellentuniformity results can be obtained on the new seed layer, even on thefirst attempt at electroplating.

In the second case noted above, an update of or selection of anotherstored sensitivity/Jacobian matrix can be used to account for asignificantly different resistance of the seed-layer. A simple method toadjust for the new seed layer thickness is to plate a film onto the newseed layer using the same currents used in plating a film on theprevious seed layer. The thickness errors measured from this wafer canbe used with a sensitivity matrix appropriate for the new seed-layer toadjust the currents.

To further illuminate the operation of the optimizer, a second test runis described. In the second test run, the optimization process beginswith a baseline current set or standard recipe currents. A wafer must bepre-read for seed layer thickness data, and then plated using theindicated currents. After plating, the wafer is re-measured for thefinal thickness values. The following wafer must also be pre-read forseed layer thickness data. Sixty-seven points at the standard fiveradial positions (0 mm, 31.83 mm, 63.67 mm 80 mm, 95.5 mm) are typicallymeasured and averaged for each wafer reading.

The thickness data from the previous wafer, and the new wafer seedlayer, in addition to the anode currents, are entered into the inputpage of the optimizer. The user may also elect to input a thicknessspecification, or chose to modify the plating thickness by adjusting thetotal current in amp-minutes. After all the data is correctly inputted,the user activates the optimizer. In response, the optimizer predictsthickness changes and calculates new currents.

The new wafer is then plated with the adjusted anode currents and thenmeasured. A second modification may be required if the thickness profileis not satisfactory.

When a further iteration is required, the optimization is continued. Asbefore, the post-plated wafer is measured for thickness values, andanother wafer is pre-read for a new seed set of seed layer thicknessvalues. Then, the following quantities are entered on the input page:

-   -   1. plated wafer thickness,    -   2. anode currents,    -   3. plated wafer seed layer thickness, and    -   4. new wafer seed layer thickness

The recipe time and thickness profile specification should be consistentwith the previous iteration. The program is now ready to be run again toprovide a new set of anode currents for the next plating attempt.

After plating with the new currents, the processed wafer is measured andif the uniformity is still not acceptable, the procedure may becontinued with another iteration. The standard value determining theuniformity of a wafer is the 3-σ, which is the standard deviation of themeasured points relative to the mean and multiplied by three. Usually aforty-nine point map is used with measurements at the radial positionsof approximately 0 mm, 32 mm, 64 mm, and 95 mm to test for uniformity.

The above procedure will be demonstrated using a multi-iterationexample. Wafer #3934 is the first plated wafer using a set of standardanode currents: 0.557/0.818/1.039/0.786 (anode1/anode2/anode3/anode4 inamps) with a recipe time of 2.33 minutes (140 seconds). Before plating,the wafer is pre-read for seed layer data. These thickness values, inmicrons, from the center to the outer edge, are shown in Table 3: TABLE3 SEED LAYER THICKNESS VALUES FOR WAFER #3934 Radius (mm) Thickness (μm)0.00 0.130207 31.83 0.13108 63.67 0.131882 80.00 0.129958 95.50 0.127886

The wafer is then sent to the plating chamber, and then re-measuredafter being processed. The resulting thickness values (in microns) forthe post-plated wafer #3934 are shown in Table 4: TABLE 4 THICKNESSVALUES FOR POST-PLATED WAFER #3934 Radius (mm) Thickness (μm) 0.000.615938 31.83 0.617442 63.67 0.626134 80.00 0.626202 95.50 0.628257

The 3-σ for the plated wafer is calculated to be 2.67% over a range of230.4 Angstroms. Since the currents are already producing a wafer below3%, any adjustments are going to be minor. The subsequent wafer has tobe pre-read for seed layer values in order to compensate for any seedlayer differences. Wafer #4004 is measured and the thickness values inmicrons are shown in Table 5: TABLE 5 SEED LAYER THICKNESS VALUES FORWAFER #4004 Radius (mm) Thickness (μm) 0.00 0.130308 31.83 0.13117863.67 0.132068 80.00 0.13079 95.50 0.130314

For this optimization run, there is no thickness profile specification,or overall thickness adjustment. All of the preceding data is inputtedinto the optimizer, and the optimizer is activated to generate a new setof currents. These currents will be used to plate the next wafer. FIG. 6is a spreadsheet diagram showing the new current outputs calculated fromthe inputs for the first optimization run. It can be seen that the inputvalues 601 have generated output 602, including a new current set. Theoptimizer has also predicted the absolute end changed thicknesses 603that this new current set will produce.

The new anode currents are sent to the process recipe and run in theplating chamber. The run time and total currents (amp-minutes) remainconstant, and the current density on the wafer is unchanged. The newseed layer data from this run for wafer #4004 will become the old seedlayer data for the next iteration.

The thickness (microns) resulting from the adjusted currents plated onwafer #4004 are shown in Table 6: TABLE 6 THICKNESS VALUES FORPOST-PLATED WAFER #4004 Radius (mm) Thickness (μm) 0.00 0.624351 31.830.621553 63.67 0.622704 80.00 0.62076 95.50 0.618746

The post-plated wafer has a 3-σ of 2.117% over a range of 248.6Angstroms. To do another iteration, a new seed layer measurement isrequired, unless notified that the batch of wafers has equivalent seedlayers. Wafer #4220 is pre-measured and the thickness values in micronsare shown in Table 7: TABLE 7 SEED LAYER THICKNESS VALUES FOR WAFER#4220 Radius (mm) Thickness (μm) 0.00 0.127869 31.83 0.129744 63.670.133403 80.00 0.134055 95.50 0.1335560

Again, all of the new data is inputted into the optimizer, along withthe currents used to plate the new wafer and the thickness of the platedwafer's seed. The optimizer automatically transfers the new currentsinto the old currents among the inputs. The optimizer is then activatedto generate a new set of currents. FIG. 7 is a spreadsheet diagramshowing the new current outputs calculated from the inputs for thesecond optimization run. It can be seen that, from input value 701, theoptimizer has produced output 702 including a new current set. It canfurther be seen that that the facility has predicted absolute andchanged thicknesses 703 that will be produced using the new currents.

The corrected anode currents are again sent to the recipe and applied tothe plating process. The 2^(nd) adjustments on the anode currentsproduce the thickness values in microns shown in Table 8: TABLE 8THICKNESS VALUES FOR POST-PLATED WAFER #4220 Radius (mm) Thickness (μm)0.00 0.624165 31.83 0.622783 63.67 0.626911 80.00 0.627005 95.500.623823

The 3-σ for wafer #4220 is 1.97% over a range of 213.6 Angstroms. Theprocedure may continue to better the uniformity, but the for the purposeof this explanation, a 3-σ below 2% is acceptable.

The optimizer may also be used to compensate for reactor-to-reactorvariations in a multiple reactor system, such as the LT-210C™ availablefrom Semitool, Inc., of Kalispell, Mont. In such a system, there is apossibility that the anode currents required to plate a specified filmmight be different on one reactor when compared to another. Somepossible sources for such differences include variations in the waferposition due to tolerances in the lift-rotate mechanism, variations inthe current provided to each anode due to power supply manufacturingtolerances, variations in the chamber geometry due to manufacturingtolerances, variations in the plating solution, etc.

In a single anode system, the reactor-to-reactor variation is typicallyreduced either by reducing hardware manufacturing tolerances or bymaking slight hardware modifications to each reactor to compensate forreactor variations. In a multiple anode reactor constructed inaccordance with the teachings of the present invention,reactor-to-reactor variations can be reduced/eliminated by runningslightly different current sets in each reactor. As long as the reactorvariations do not fundamentally change the system response (i.e., thesensitivity matrix), the self-tuning scheme disclosed herein is expectedto find anode currents that meet film thickness targets.Reactor-to-reactor variations can be quantified by comparing differencesin the final anode currents for each chamber. These differences can besaved in one or more offset tables in the control system 65 so that thesame recipe may be utilized in each reactor. In addition, these offsettables may be used to increase the efficiency of entering new processingrecipes into the control system 65. Furthermore, these findings can beused to trouble-shoot reactor set up. For example, if the values in theoffset table are over a particular threshold, the deviation may indicatea hardware deficiency that needs to be corrected.

As mentioned above, embodiments of the optimizer may be used to setcurrents and other parameters for complex deposition recipes thatspecify changes in current during the deposition cycle. As an example,embodiments of the optimizer may be used to determine anode currents inaccordance with recipe having two different steps. Step 1 of the recipelasts for 0.5 minutes, during which a total of +1 amp of current isdelivered through four electrodes. Step 2 of the recipe, whichimmediately follows step 1, is 1.25 minutes long. During step 2, a totalcurrent of +9 amps is delivered for 95 milliseconds. Immediatelyafterwards, a total current of −4.3 amps is delivered for 25milliseconds. Ten milliseconds after delivery of the −4.3 amp current isconcluded, the cycle repeats, delivering +9 amps for another 95milliseconds. The period during which a positive current is beingdelivered is known as the “forward phase” of the step, while the timeduring which a negative current is being delivered is known as the“backward phase” of the step. Backward phases may be used, for example,to reduce irregularities formed in the plated surface as the result oforganic substances within the plating solution.

In order to apply the optimizer to optimize currents for this recipe,initial currents are chosen in accordance with the recipe. These areshown below in Table 9. TABLE 9 Initial Multi-step Recipe Step 1 Step2 1. time 0.5 1.25 2. forward fraction 1 0.730769 3. anode 1 current 0.21.8 4. anode 2 current 0.24 2.16 5. anode 3 current 0.34 3.06 6. anode 4current 0.22 1.98 7. backward fraction 0.192307 8. anode 1 current −0.869. anode 2 current −1.03 10. anode 3 current −1.46 11. anode 4 current−0.95 12. forward amp-min 0.5 8.221153 13. backward amp-min 0 −1.03365314. Total Amp-min 7.6875

The left-hand column of Table 9 shows currents and other information forthe first step of the recipe, while the right-hand column shows currentsand other information for the second step of the recipe. In line 1, itcan be seen that step 1 has a duration of 0.5 minutes, while step 2 hasa duration of 1.25 minutes. In line 2, it can be seen that, in step 1,forward plating is performed for 100% of the duration of the step, whilein step 2, forward plating is performed for about 73% of the duration ofthe step (95 milliseconds out of the 130 millisecond period of thestep). Lines 3-6 show the currents delivered through each of the anodesduring the forward phase of each of the two steps. For example, it canbe seen that 0.24 amps are delivered through anode 2 for the duration ofstep 1. In line 7, it can be seen that a negative current is deliveredfor about 19% of the duration of step 2 (25 milliseconds out of thetotal period of 130 milliseconds). Lines 8-11 show the negative currentsdelivered during the backward phase of step 2. Line 12 shows the charge,in amp-minutes, delivered in the forward phase of each step. For step 1,this is 0.5 amp-minutes, computed by multiplying the step 1 duration of0.5 minutes by the forward fraction of 1, and by the sum of step 1forward currents, 1 amp. The forward plating charge for step 2 is about8.22 amp-minutes, computed by multiplying the duration of step 2, 1.25minutes, by the forward fraction of about 73%, and by the sum of theforward currents in step 2, 9 amps. Line 13 shows the results of asimilar calculation for the backward phase of step 2. Line 14 shows thenet plating charge, 7.6875 amp-minutes obtained by summing the signedcharge values on lines 12 and 13.

The deposition chamber is used to deposit a wafer in accordance withthese initial currents. That is, during the first half-minute ofdeposition (step 1), +0.2 amps are delivered through anode 1. During thenext 1.25 minutes of the process (step 2), +1.8 amps are deliveredthrough anode 1 for 95 milliseconds, then −0.86 amps are deliveredthrough anode 1 for 25 milliseconds, then no current flows through 1 for10 milliseconds, and then the cycle is repeated until the end of the1.25 minute duration of step 2. Overall, the charge of 1.537 amp-minutesis delivered through anode 1. This value is determined by multiplyingduration, forward fraction, and anode 1 current from step 1, then addingthe product of the duration of step 2, the forward fraction of step 2,and the forward anode 1 current of step 2, then adding the product ofthe duration of step 2, the backward fraction of step 2, and thebackward anode 1 current of step 2. Such net plating charges may becalculated for each of the anodes, as shown below in Table 10. TABLE 10Net Plating Charges in Initial Multi-step Recipe Anode1 1.537 Amp-minAnode2 1.845 Amp-min Anode3 2.614 Amp-min Anode4 1.690 Amp-min

These plating charge values are submitted to the optimizer together withthicknesses measured from the wafer plated using the initial current. Inresponse, the optimizer generates a set of new net plating charges foreach electrode. These new net plating charges are shown below in Table11. TABLE 11 New Net Plating Charges for Revised Recipe Anode1 1.537Amp-min + 0.171286 Amp-min = 1.709 Amp-min Anode2 1.845 Amp-min −0.46657 Amp-min = 1.379 Amp-min Anode3 2.614 Amp-min + 0.106337 Amp-min= 1.271 Amp-min Anode4 1.690 Amp-min + 0.188942 Amp-min = 1.879 Amp-min

The optimizer then computes for each anode a share of the current to bedelivered through the anode by dividing the new net plating chargedetermined for the anode by the sum of the net plating chargesdetermined for all of the anodes. These current shares are shown belowin Table 12. TABLE 12 Current Shares for Revised Recipe Anode11.709/7.6875 = 22.2% Anode2 1.379/7.6875 = 17.9% Anode3 1.271/7.6875 =35.5% Anode4 1.879/7.6875 = 24.4%

The optimizer then determines a new current for each anode in each stepand phase of the recipe by multiplying the total current for the stepand phase by the current share computed for each anode. These are shownin Table 13 below. TABLE 13 Revised Multi-Step Recipe Step 1 Step 2 1.time 0.5 1.25 2. forward fraction 1 0.730769 3. anode 1 current 0.2222812.000530 4. anode 2 current 0.179371 1.614339 5. anode 3 current0.353895 3.185055 6. anode 4 current 0.244452 2.200075 7. backwardfraction 0.192307 8. anode 1 current 0 −0.955808 9. anode 2 current 0−0.771295 10. anode 3 current 0 −1.521748 11. anode 4 current 0−1.051147 12. forward amp-min 0.5 8.221153 13. backward amp-min 0−1.033653 14. Total Amp-min 7.6875

For example, it can be seen in line 4 of Table 13 that the forward anode2 current for step 2 is about 1.61 amps, computed by multiplying the +9amps total current for the forward phase of step 2 by the current shareof 17.9% computed for anode 2 shown in Table 12.

By comparing Table 13 to Table 9, it can be seen that the net platingcharge changes specified by the optimizer for the revised recipe aredistributed evenly across the steps and phases of this recipe. It canalso be seen that the total plating charge for each step and phase ofthe revised recipe, as well as the total plating charge, is unchangedfrom the initial multistep recipe. The optimizer may utilize variousother schemes for distributing plating charge changes within the recipe.For example, it may alternatively distribute all the changes to step 2of the recipe, leaving step 1 of the recipe unchanged from the initialmulti-step recipe. In some embodiments, the optimizer maintains andapplies a different sensitivity matrix for each step in a multi-steprecipe.

In some embodiments, the facility utilizes a form of predictive controlfeedback. In these embodiments, the optimizer generates, for each set ofrevised currents, a set of predicted plating thicknesses. The optimizerdetermines the difference between these predicted thicknesses and theactual plated thicknesses of the corresponding workpiece. For eachworkpiece, this set of differences represents the level of errorproduced by the optimizer in setting currents for the workpiece. Theoptimizer uses the set of differences for the previous workpiece toimprove performance on the incoming workpiece by subtracting thesedifferences from the target thickness changes to be effected by currentchanges for the incoming workpiece. In this way, the optimizer is ableto more quickly achieve the target plating profile.

Further sample wafer processing processes employing the optimizer arediscussed below. It should be noted that no attempt is made toexhaustively list such processes, and that those included are merelyexemplary.

Table 13 below shows a sample wafer processing process employing theoptimizer, from which a subset of the steps may be selected and/ormodified to define additional such processes. TABLE 13 Sample WaferProcessing Process Employing Optimizer Step Tool/Process 1. Depositmetal seed layer using one or more physical vapor deposition (“PVD”)tools, different chambers on the same PVD tool, or CVD chambers orelectroless deposition chambers. 2. Measure seed layer film thicknessusing metrology station, either on the tool or an independent station -metrology stations can infer film thickness from sheet resistancemeasurements or from optical measurements of the film 3. Applyoptimizer - residing on tool or off tool on a personal computer - in aseed layer enhancement (“SLE”) chamber using measurements from step 2(feedforward) and measurement results from previous SLE wafer on step 6or 8 (feedback) 4. Deposit metal layer in SLE chamber 5. Rinse wafer inSRD/Capsule chamber 6. Measure wafer thickness using Metrology Station7. Anneal wafer in annealing chamber on the tool or in independentstations 8. Measure wafer thickness using Metrology Station 9. Applyoptimizer in ECD chamber using measurements from step 7 (feedforward)and measurement results from previous ECD wafer on step 12 or 14(feedback) 10. Deposit final metal layer in ECD chamber 11. Clean andbevel etch wafer in Capsule chamber 12. Measure wafer thickness usingMetrology Station 13. Anneal wafer in anneal chamber 14. Measure waferthickness using Metrology Station

These steps may be qualified in a variety of ways including: themeasurement/optimizer sequence steps can be performed during toolqualification or “dial-in”; the measurement/optimizer sequence stepssequence can be performed periodically to monitor performance; themeasurement/optimizer sequence steps sequence can be performed on eachwafer; SLE process may be optional depending upon the measurementresults in step 2 (i.e., this wafer may routed around this andassociated process steps); wafer sequence may be terminated, rerouted,or restarted based upon the measurement results of step 2, 6, 8, 12, and14; measurement/optimizer steps may be performed only afterprocess/hardware changes; measurements before and after annealing (e.g.,sheet resistance) may be used to determine effectiveness of annealingprocess; metal deposition steps 4 and 10 may be deposition of samemetals or different metals—they could deposit the same metal usingdifferent baths; one or more metal deposition steps could be used, whichdeposit one or more different metals; the optimization steps may adjustcurrents to generate a flat thickness profile or one with a specifiedshape; the optimization steps may adjust current to generate a desiredcurrent density profile for future filling; the wafer may be returned toa deposition chamber for additional metal deposition if the filmthickness is insufficient, based upon metrology results.

Table 14 below shows an additional sample process: TABLE 14 Sample WaferProcessing Process Employing Optimizer Step Tool/Process 1. Depositmetal seed layer using PVD tool 2. Measure seed layer film thicknessusing metrology station 3. Apply optimizer in ECD chamber usingmeasurements from step 2 (feedforward) and measurement results fromprevious ECD wafer on step 7 (feedback) 4. Deposit final metal layer inECD chamber 5. Anneal wafer in anneal chamber 6. Clean and bevel etchwafer in Capsule chamber 7. Measure wafer thickness using MetrologyStation

Table 15 below shows an additional sample process: TABLE 15 Sample WaferProcessing Process Employing Optimizer Step Tool/Process 1. Depositmetal seed layer using PVD tool 2. Measure seed layer film thicknessusing metrology station 3. Apply optimizer in ECD chamber usingmeasurements from step 2 (feedforward) and measurement results fromprevious ECD wafer on step 6 (feedback) 4. Deposit final metal layer inECD chamber 6. Clean and bevel etch wafer in Capsule chamber 7. Measurewafer thickness using Metrology Station

Table 16 below shows an additional sample process: TABLE 16 Sample WaferProcessing Process Employing Optimizer Step Tool/Process 1. Depositmetal seed layer using PVD tool 2. Measure seed layer film thicknessusing metrology station 3. Apply optimizer in ECD chamber usingmeasurements from step 2 (feedforward) and measurement results fromprevious SLE wafer on step 6 (feedback) 4. Deposit metal layer in SLEchamber 6. Clean and bevel etch wafer in Capsule chamber 7. Measurewafer thickness using Metrology Station

As an additional sample process, the thickness uniformity of a waferwith a PVD-deposited seed layer is measured on a dedicated metrologytool, after which the wafer is brought to the plating tool and placed inan SLE process chamber. Using the measurements from the dedicatedmetrology tool, the optimizer is used to select an SLE recipe that willaugment the PVD-deposited seed layer to yield a seed layer with improvedthickness uniformity, and the SLE process is performed on the wafer.After the wafer has been cleaned and dried in one of the plating toolcapsule chambers, the wafer is transferred to a plating chamber wherethe optimizer is then used to select a plating recipe that will yield auniform bulk film, at the desired thickness, based on the nominal seedlayer thickness. After the bulk film plating process has completed, thewafer is transferred to a capsule cleaning chamber, whereupon it isremoved from the tool.

As an additional sample process, a wafer is brought to the plating tooland placed in the on-board metrology station to determine the thicknessprofile of the CVD-deposited seed layer. The wafer is then transferredto a plating chamber. Using the seed layer measurements from theon-board metrology station, the optimizer is used to select a platingrecipe that will yield a convex (center-thick) bulk film, at the desirednominal thickness. After the plating process has completed, the wafer istransferred to a capsule cleaning chamber, whereupon it is removed fromthe tool.

As an additional sample process, a wafer comes to an electroplating toolwith a seed layer, applied using physical vapor deposition, that isnon-uniform. A metrology station is used to measure the non-uniformity,and the optimizer operates the multiple-electrode reactor to correct themeasured non-uniformity. Seed layer repair is then performed using anelectroless ion plating process to produce a final, more uniform, seedlayer. The optimizer then operates to deposit bulk metal onto therepaired seed layer.

As an additional sample process, a semiconductor fabricator has twophysical vapor deposition tools (“PVD tools”), each of which has its ownparticular characteristics. A wafer processed by the first PVD tool andhaving a seed layer non-uniformity is directed to a firstmultiple-electrode reactor for seed layer repair. A wafer from thesecond PVD tool that has a different seed layer non-uniformity isdirected to a second multiple-electrode reactor for seed layer repair.Bulk metal is then deposited onto the repaired seed layers of the twowafers in a third CFD reactor under the control of the optimizer.

Additional applications of the optimizer include:

Single plating example: The production environment can involve manyrecipes on a tool because each wafer may require multiple processingsteps. For example, there may be 5-7 metal interconnect layers and eachof the layers have different process parameters. Furthermore, a tool maybe processing several different products. The advantage having amultiple anode reactor on the tool (like the CFD reactor) is that uniqueanode currents and optimal performance may be specified for all thedifferent recipes on all the different chambers on the tool.

A basic application of the optimizer is to aid in the initial dial-inprocess for all of the recipes that are going to be run on a tool inproduction. In this mode, recipes will be written and testedexperimentally prior to production, using the optimizer as an aid toobtained uniformity specifications. In this picture of workpieceproduction, the optimizer is used during the set-up phase only, savingthe process engineer much time in setting up the tool and each of therecipes. If seed-layers coming into the tool are identical and stable,the above picture is sufficient.

If the seed-layers are not consistent, then off-tool metrology orintegrated metrology can be used to monitor the changes in theseed-layers and the optimizer can be used to modify the anode currentsin the recipe to compensate for these variations.

ECD seed followed by bulk ECD: In the case of sequential plating steps,metrology before and after each plating step allows for recipe currentadjustments with the optimizer to each process. In the case of ECD seed,the initial PVD or CVD layer of metal can be measured and adjusted forusing the feed-forward feature of the optimizer. Note: In this processthe resistance of the barrier layer under the seed layer can also have alarge influence on the plating uniformity, if the resistance of thislayer can be measured, then the optimizer can be used to compensate forthis effect (it may take more than one iteration of the optimizer).

Dial-In Uniform Current Density Recipes: Using the optimizer andmetrology the optimizer can be used to help dial in recipes that insureuniform current density during the feature filling step.

Table Look-Up: The optimal currents to plate uniformly on differentthickness seed-layers (assuming the seed layers are substantiallyuniform) can be determined in advance, using the optimizer to find thesecurrents. Then the currents can be pulled from a table, when theresistivity of the seed layer is measured. This may be quite useful forplaten plating (solder) where the seed layer resistance is constant forthe whole plating run.

It is envisioned that the optimizer may be used in one or more stages ofwidely-varying processes for processing semiconductor workpieces. It isfurther envisioned that the optimizer may operate completely separatelyfrom the processing tools performing such processes, with only somemechanism for the optimizer to pass control parameters to suchprocessing tools. Indeed, the optimizer and processing tools may beoperated under the control and/or ownership of different parties, and/orin different physical locations.

Numerous modifications may be made to the described optimizer withoutdeparting from the basic teachings thereof. For example, although thepresent invention is described in the context of electrochemicalprocessing of the microelectronic workpiece, the teachings herein canalso be extended to other types of microelectronic workpiece processing,including various kinds of material deposition processes. For example,the optimizer may be used to control electrophoretic deposition ofmaterial, such as positive or negative electrophoretic photoresists orelectrophoretic paints; chemical or physical vapor deposition; etc. Ineffect, the teachings herein can be extended to other microelectronicworkpiece processing systems that have individually controlledprocessing elements that are responsive to control parameters and thathave interdependent effects on a physical characteristic of themicroelectronic workpiece that is processed using the elements. Suchsystems may employ sensitivity tables or matrices as set forth hereinand use them in calculations with one or more input parameters sets toarrive at control parameter values that accurately result in thetargeted physical characteristic of the microelectronic workpiece.Although the present invention has been described in substantial detailwith reference to one or more specific embodiments, those of skill inthe art will recognize that changes may be made thereto withoutdeparting from the scope and spirit of the invention as set forthherein.

1-100. (canceled)
 101. A method for electrolytically processing amicroelectronic workpiece using a processing chamber, a first electrodein the processing chamber, and a second electrode concentric with thefirst electrode in the processing chamber, comprising: contacting thesurface of the microelectronic workpiece with an electrolytic fluid inthe processing chamber; filling features in the workpiece by deliveringa first initial current to the first electrode and a second initialcurrent to the second electrode during a first stage of a plating cyclefor the workpiece; and depositing additional material onto the workpieceduring a second stage of the plating cycle by delivering a first bulkplating current to the first electrode and a second bulk plating currentto the second electrode, wherein the first initial current is differentthan the first bulk plating current and the second initial current isdifferent than the second bulk plating current.
 102. The method of claim101 wherein the first initial current is less than the first bulkplating current and the second initial current is less than the secondbulk plating current.
 103. The method of claim 101, further comprisingdelivering the first initial current and the second initial current toprovide at least a substantially uniform current density at the surfaceof the workpiece.
 104. The method of claim 103, further comprisingdelivering the first bulk plating current and the second bulk platingcurrent to provide a bulk plated layer on the workpiece having asubstantially uniformly flat thickness profile across the surface of theworkpiece.
 105. The method of claim 103, further comprising deliveringthe first bulk plating current and the second bulk plating current toprovide a bulk plated layer on the workpiece having a convex thicknessprofile that is thicker at the center of the workpiece than at theperimeter of the workpiece.
 106. The method of claim 101 wherein thefirst initial current is greater than the second initial current, andwherein the first bulk plating current is greater than the second bulkplating current.
 107. The method of claim 101 wherein the first initialcurrent is less than the second initial current, and wherein the firstbulk plating current is less than the second bulk plating current. 108.A method for electrolytically processing a microelectronic workpieceusing a processing chamber, a first electrode in the processing chamber,and a second electrode concentric with the first electrode in theprocessing chamber, comprising: contacting the surface of themicroelectronic workpiece with an electrolytic fluid in the processingchamber; delivering a first set of electrical currents through the firstand second electrodes during a first stage of a plating cycle for theworkpiece; and changing the first set of electrical currents to delivera second set of electrical currents through the first and secondelectrodes during a second stage of the plating cycle for the workpiece,wherein the first set of electrical currents is less than the second setof electrical currents.
 109. The method of claim 108, wherein: the firstset of electrical currents includes a first initial current deliveredthrough the first electrode and a second intial current deliveredthrough the second electrode; and the second set of electrical currentsincludes a first subsequent current delivered through the firstelectrode and a second subsequent current delivered through the secondelectrode.
 110. The method of claim 109 wherein the first initialcurrent is less than the first subsequent current and the second initialcurrent is less than the second subsequent current.
 111. The method ofclaim 108, further comprising delivering the first set of electricalcurrents to provide at least a substantially uniform current density atthe surface of the workpiece.
 112. The method of claim 108, furthercomprising delivering the second set of electrical currents to provide abulk plated layer on the workpiece having a substantially uniformly flatthickness profile across the surface of the workpiece.
 113. The methodof claim 108, further comprising delivering the second set of electricalcurrents to provide a bulk plated layer on the workpiece having a convexthickness profile that is thicker at the center of the workpiece than atthe perimeter of the workpiece.
 114. A method for electrolyticallyprocessing a microelectronic workpiece using a processing chamber, afirst electrode in the processing chamber, and a second electrodeconcentric with the first electrode in the processing chamber,comprising: contacting the surface of the microelectronic workpiece withan electrolytic fluid in the processing chamber; producing a uniformcurrent density at the surface of the workpiece to deposit an initiallayer onto the workpiece during an intial stage of a plating cycle bydelivering a first initial current through the first electrode anddelivering a second initial current through the second electrode; andforming a profiled layer on the initial layer during a subsequent stageof the plating cycle by delivering a first profile current through thefirst electrode and delivering a second profile current through thesecond electrode, wherein the first initial current is different thanthe first profile current and the second initial current is differentthan the second profile current.
 115. The method of claim 114 whereinthe first and second initial currents are delivered through the firstand second electrodes, respectively, while plating into micro-featureson the workpiece.
 116. The method of claim 115 wherein first and secondprofile currents are delivered through the first and second electrodes,respectively, to form a profiled layer having a substantially uniformthickness across the workpiece.
 117. The method of claim 115 wherein thefirst and second profile currents are delivered through the first andsecond electrodes, respectively, to form a profiled layer having aconvex thickness profile such that profiled layer is thicker at acentral portion of the workpiece than at a perimeter portion of theworkpiece.